Scotland does not have that many marginal seats: Labour won 40 out of 59 seats in 2005, the Conservatives a solitary one (up from zero in 1997); there are only two Conservative/Labour seats the Tories have any realistic chance of winning – Dumfries and Galloway, and Stirling.

All of this has the effect of making a UK election in Scotland a slightly surreal, semi-detached affair, where the sounds of the cannon fire can be heard, but in a far-off battlefield. This contributes to the slow attrition and dilution of Scotland's bonds in the union.

Scottish politics have a different shape and direction to UK politics. Scotland has a four-party system, rather than the UK's two-and-a-half party system. First-past-the-post contributes to the Westminster adversarial system, whereas Scotland has different proportional representation systems for every layer of government – apart from Westminster.

More crucial is the cumulative divergence between Scotland and Westminster on policy. New Labour has pursued market reforms south of the border on public services with city academies, foundation hospitals, privatisation and the "choice" mantra. Scottish Labour, and then the SNP, in Holyrood have gone down a very different route, emphasising partnership and equity rather than efficiency.

This divergence would accelerate even more if the Conservatives are elected with their plans for handing over large parts of the NHS and public services to the McKinsey state. This is one important way in which Scotland and England slowly and quietly become not just more different nations, but places shaped by very different sets of values.

The election also promises to bring back constitutional issues and the prospect for conflict. If the Conservatives win, they will do so with a Scottish vote of less than 20% and, at best, two to three seats. Scotland is the one part of the UK with no visible "Cameron bounce". This will, in a Groundhog Day way, bring Scotland screaming back to the 1980s and what used to be called "the doomsday scenario" – which was an explanation of Scotland voting Labour and getting a Tory government.

The establishment of the Scottish parliament was meant to address these concerns. But, of course, it isn't within its powers to do so. And as long as England continues to vote Tory in such numbers, as it looks likely, this problem will continue.

Two future scenarios are possible. The first, a Conservative majority government, would illustrate the party's lack of Scottish appeal while holding monopoly power at Westminster. The second, a Conservative minority government, would highlight that this would be a mandate based on English votes and seats, and that Scotland and Wales with their Labour representation had made the election much closer.

This would have two likely consequences. The first would be to bring the issue of Scottish representation in the Commons to the fore, and the prospect of the Tories legislating to further reduce Scots representation, or even consider "English votes for English laws". The second would be to raise the issue of the English dimension, the last huge democratic vacuum at the heart of the UK. Scotland, Wales and Northern Ireland have all developed their collective voices through devolution, and England has not even begun to work out whether it wants to have a specifically English voice.

The UK election has the distinct prospect of pushing the English towards thinking about this. Whatever happens, the gradual fragmentation of the UK is going to continue. The Scottish campaign, and what happens afterwards, will be an important component of this, whatever Gordon Brown and David Cameron say and do today, and over the rest of the campaign.

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